c# - C#UDP套接字: Get receiver address

我有一个异步UDP服务器类，其套接字绑定(bind)在IPAddress.Any上，我想知道接收到的数据包发送到(或接收到)哪个IPAddress。似乎我不能只使用Socket.LocalEndPoint属性，因为它总是返回0.0.0.0(这与它绑定(bind)在一起是有道理的...)。

这是我当前正在使用的代码中有趣的部分:

private Socket udpSock;
private byte[] buffer;
public void Starter(){
    //Setup the socket and message buffer
    udpSock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
    udpSock.Bind(new IPEndPoint(IPAddress.Any, 12345));
    buffer = new byte[1024];

    //Start listening for a new message.
    EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
    udpSock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref newClientEP, DoReceiveFrom, udpSock);
}

private void DoReceiveFrom(IAsyncResult iar){
    //Get the received message.
    Socket recvSock = (Socket)iar.AsyncState;
    EndPoint clientEP = new IPEndPoint(IPAddress.Any, 0);
    int msgLen = recvSock.EndReceiveFrom(iar, ref clientEP);
    byte[] localMsg = new byte[msgLen];
    Array.Copy(buffer, localMsg, msgLen);

    //Start listening for a new message.
    EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
    udpSock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref newClientEP, DoReceiveFrom, udpSock);

    //Handle the received message
    Console.WriteLine("Recieved {0} bytes from {1}:{2} to {3}:{4}",
                      msgLen,
                      ((IPEndPoint)clientEP).Address,
                      ((IPEndPoint)clientEP).Port,
                      ((IPEndPoint)recvSock.LocalEndPoint).Address,
                      ((IPEndPoint)recvSock.LocalEndPoint).Port);
    //Do other, more interesting, things with the received message.
}

如前所述，它总是打印一行:

我希望它像是:

预先感谢您对此有任何想法!
- 亚当

更新

好吧，我找到了一个解决方案，尽管我不喜欢它...基本上，不是打开绑定(bind)到IPAddress的单个udp套接字，而是为每个可用的IPAddress创建一个唯一的套接字。因此，新的Starter函数如下所示:

public void Starter(){
    buffer = new byte[1024];

    //create a new socket and start listening on the loopback address.
    Socket lSock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
    lSock.Bind(new IPEndPoint(IPAddress.Parse("127.0.0.1"), 12345);

    EndPoint ncEP = new IPEndPoint(IPAddress.Any, 0);
    lSock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref ncEP, DoReceiveFrom, lSock);

    //create a new socket and start listening on each IPAddress in the Dns host.
    foreach(IPAddress addr in Dns.GetHostEntry(Dns.GetHostName()).AddressList){
        if(addr.AddressFamily != AddressFamily.InterNetwork) continue; //Skip all but IPv4 addresses.

        Socket s = new Socket(addr.AddressFamily, SocketType.Dgram, ProtocolType.Udp);
        s.Bind(new IPEndPoint(addr, 12345));

        EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
        s.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref newClientEP, DoReceiveFrom, s);
    }
}

这只是为了说明概念，此代码的最大问题是，每个套接字都试图使用相同的缓冲区...这通常是个坏主意...

必须对此有一个更好的解决方案。我的意思是，源和目标是UDP数据包头的一部分!哦，好吧，我想我会继续研究，直到有更好的东西为止。

最佳答案

我只是有同样的问题。我看不到使用ReceiveFrom或其异步变体检索接收到的数据包的目标地址的方法。

但是...如果使用ReceiveMessageFrom或其变体，您将获得IPPacketInformation(通过引用ReceiveMessageFrom和EndReceiveMessageFrom或作为SocketAsyncEventArgs的属性传递给ReceiveMessageFromAsync的回调)。该对象将包含接收数据包的IP地址和接口(interface)号。

(请注意，此代码尚未经过测试，因为我使用了ReceiveMessageFromAsync而不是假冒的Begin/End调用。)

private void ReceiveCallback(IAsyncResult iar)
{
    IPPacketInformation packetInfo;
    EndPoint remoteEnd = new IPEndPoint(IPAddress.Any, 0);
    SocketFlags flags = SocketFlags.None;
    Socket sock = (Socket) iar.AsyncState;

    int received = sock.EndReceiveMessageFrom(iar, ref flags, ref remoteEnd, out packetInfo);
    Console.WriteLine(
        "{0} bytes received from {1} to {2}",
        received,
        remoteEnd,
        packetInfo.Address
    );
}

注意，显然，应该在设置SetSocketOption(SocketOptionLevel.IP, SocketOptionName.PacketInformation, true)之前调用Bind作为设置套接字的一部分。 ... ReceiveMessageFrom ...方法将为您设置它，但是设置该选项后，您可能只会看到Windows看到的任何数据包的有效信息。 (实际上，这不是什么大问题-但是何时/如果发生过，原因将是一个谜。最好完全避免它。)

关于c# - C#UDP套接字: Get receiver address，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/4147542/